Billet or blank suitable for the production of turbine blades



I flg- 1930. c. A. PARSONS E AL BILLET OR BLANK SUITABLE FOR THE PRODUCTION OF TURBINE BLADES Filed Aug. 14. 1928 Patented Aug. 12, 1930 CHARLES ALGERNON PARSONS AND EDWARD GARRETT IBROVVNLOVV, OF NEWCASTLE- ON-TYNE, ENGLAND"; SAID BEOWNLOYV ASSIGNOR TO SAID PARSDNS BILLET OR BLANK SUITABLE :FOR THE PRODUCTION OF TURBINE BLADES Application filed August 14, 1928, Serial No. 299,555, andin Great'IBritain Noveinlier 7, 192?.

larly applicable to turbine-blade billets havwhile ing an integral root-forming portion.

In the specific application indicated, such a billet may take, for eXample, the form of a T of uniform thickness, the cross of the T in general approximating to the final form of blade root desired while the stem, which may be of considerable length in comparison with the cross, is extended and shaped as by rolling to form the blade proper. 1

In order to avoid too abrupt a change in cross-section between the finished blade and its integral root, it is desirable that the thickness of the blade proper shall gradually increase towards the root and consequently at this point less deformation is required in the rolling or shaping operation than at other points of the blade length and extra material is required at the point of junction to allow for the thicker section. Such additional material has usually been provided in the form of fillets where the blade-forming portion of the billet joins the root-forming portion.

It is found by experience, however, that when such billets are rolled, folds are formed, particularly where the thin edge of the blade section joins the root, and it becomes necessary to remove these folds between successive rolling operations, thus adding to the cost of and time taken in manufacturing the blades.

The main object of the present invention is to avoid the formation of such folds.

With such an object The invention consists in a billet or blank as indicated having root and stem portions, the stem portion diverging or widening towards and adjacent to the root portion in such a manner that the contour of the widening portion makes only a comparatively small angle with the length of the stem.

The invention also consists in the improved billets or blanks hereinafter described and turbine blades manufactured therefrom.

Referring to the accompanying diagrammatic drawings Figure 1 shows a plan View of a turbineblade blank as hitherto used'with quadranta fillets, I Figure 2 being acorresponding'end view;

Figures 3'and 4 show plan views of different forms of the improved turbine blade blank according to the present invention.

Figure 5 is a perspective view o f one form of finished blade with the root portionma- 'chined down to the final size and form to suit the turbine groove.

Where desirable the same reference letters are used in the different figures to denote corresponding parts.

The filleted turbine-blade billet or blank shown in Figures 1 and 2 as an example of common practice heretofore, comprises a blade-forming stem, A, and a root-forming base, B, forming a T of uniform thickness with fillets, C, C, having the form of circular arcs of 90 or thereabouts tangential to the relative parts of the root and stem. Experiments have shown that with such a blank, the formation of the folds is caused by that part of the fillet which makes the largest angle with the direction of rolling, i. e., the part between the lines X X, Y Y, more directly associated with the root of the blank, and by eliminating this part of the fillet in accordance with the present invention, the difiiculties set forth above are overcome.

In carrying the invention into effect according to the form shown in Figure 3 as applied to the manufacture of turbine blades, the blank as before is of uniform thickness throughout and has the form of a T with a comparatively short root-forming transverse portion, B, and a comparatively long bladeforming stem, A, atright angles thereto. At its free end, the sides of the stem are parallel as shown but where the stem approaches the root, the sides diverge slightly, the contour of the fillet being formed by straight lines, D, D, making only the small angle, 0:, with the length of the stem or in other words with the direction of rolling. One form of finished blade F produced by rolling the blank and machining is shown in Figure 5.

According to a modified form, (see Figure 4) the contour, E, E, of the diverging fillet may be slightly concaved, the maximum angle, B, in this case that the curved portion makes with the length of the stem corresponding to the small angle, a, between the straight lines, D, of the fillet and the stem in theprevious form of the invention.

Further, the stem of the billet or blank, if desired may be of other form than that shown.

10 Other variations may be made in the precise form of billet or blank without exceeding the scope of the invention so long as the angle or the maximum angle that the fillet eontourimakes with the length of the stem is below that at which folds begin toform.

,Inaddition to reducing the cost and time required in manufacturing the blades, the invention results in an improved turbine blade which is strengthened at the point where it joins onto the root, which is the point where the stresses are usually highest and additional strength I is most required.

' We claim 1. A billet or blank having root and stem portions suitable for the production of a turbine blade, the stem portion diverging or widening towards and adjacent to the root portion in such a manner that the contour of the widening portion makes only a comparatively small angle-with the length of the stem, substantially as and for the purpose described.

2. A billet or blank as claimedin claim 1,

'in which the widening portion or fillet has astraight-line contour, substantially as described.

.In'testimony whereof we have signedour :names to this specification.

CHARLES ALGERNON PARSONS.

. EDWARD GARRETTBROVNLOVV. 

